Microstructural Evolution and Mechanical Properties of L-PBF Aerospace Alloys: Hydride-Dehydride Ti-6AL-4V and Experimentally Heat-Treated Inconel 718
Experimental HIP and heat treatment cycles were applied to Laser Powder Bed Fusion fabricated Inconel 718 parts. Recent advances allow for rapid cooling in the HIPing chamber allowing one unit to perform HIP along with other heat treatment cycles such as solution annealing and ageing. Different cycles yield various effects on the porosity reduction as well as the growth of grain in the microstructure, consequently presented different mechanical properties. Specimens were therefore analyzed for density, microstructure, and tensile properties. In addition, the mechanical and microstructural analysis of HDH Ti-6Al-4V was performed. The high cost of GA Ti64 material is a significant cost driver in the AM process. Ti64 HDH (Hydrogenation-Dehydrogenation) is a low-cost form of titanium powder that has been recycled. Compared to its spherical GA counterpart, HDH powder is irregular in shape and larger in particle size, with a higher concentration of hydrogen. This could hinder the LPBF processes as well as the mechanical properties of the final part. However, if process parameters can be developed for this particular material, along with standardized Hot Isostatic Pressing and Annealing, one might accomplish similar mechanical properties to GA powder while reducing cost. In this study LPBF Ti64 HDH samples were fabricated, heat-treated, and HIP-ed in three different variants. They were then machined and tensile tested in accordance with ASTM E8 standard.
Varela, Jaime, "Microstructural Evolution and Mechanical Properties of L-PBF Aerospace Alloys: Hydride-Dehydride Ti-6AL-4V and Experimentally Heat-Treated Inconel 718" (2021). ETD Collection for University of Texas, El Paso. AAI28541334.